The physiological roles of astrocytes, particularly with respect to CNS function and response to injury, is one of the major interests in neurobiology. However, research in this area is complicated because of the distinct regional and functional specializations of the astrocytes. A major obstacle to the study of these cells and their functions is the lack of specific cell markers for the various astrocytic subgroups. The purpose of this proposal is to identify and characterize cell markes that are uniquely expressed by astrocytes during different functional states (e.g., developmental and injury-induced reactive states). The identification of such cell markers will provide a means to study physiological roles of astrocytes and the factors involved in gliosis. Astrocytes are characterized by their specific glial intermediate filaments (IFs). Thus, proteins associated with these IFs (IFAPs) are potential candidates for cell markers (1, manuscript included). Furthermore, IFAP expression in other cell types is also related to the functional and developmental status of the cell. The identification of IFAPs will help our understanding of astrocytic function. However glial IFAPs have not yet been identified. One object of this proposal is to identify and characterize glial IFAPs in cultured astrocytes using monoclonal antibodies produced against native glial IF preparations. Another object is to study the expression and function of these glial IFAPs in rat central nervous tissues under various functional conditions, including neonatal developmental states, as well as injury induced reactive states. Since our preliminary studies have shown that the monoclonal antibody to a known IFAP from baby hamster kidney (BHK-21) fibroblastic cells specifically labels a subgroup of GFAP+ 'reactive' rat astrocytes in primary culture, the characterization and cytological distribution of this putative glial IFAP is another important focus of this study. These studies will employ a variety of immunological, biochemical and morphological methodologies including cell culture, antibody preparation, gel electrophoresis, immunoblotting, column chromatography and immunocytochemistry. The results should provide a more objective approach to the identification of the subgroups of astrocytes and their involvement in gliosis and other possible CNS responses to injury.